4. Conclusions
4.1. Ethanol yield efficiency of the used method
For every kilogramof sugar (glucose) fermented are produced,
theoretically, 0.51 kg ethanol and 0.49 kg CO2, [8]. Or, for the
production of 1 kg of ethanol, 1.96 kg of sugars is required.
The theoretical maximum ethanol yield, derived from the
starch content of the flower stalks of the sample used is
therefore 57.3 cm3 kg1 based on dry material. The obtained
ethanol from the experiments was reduced in average to
55.8 cm3 kg1 based on dry flower stalks, with a small standard
deviation of measurements. This was due to the incomplete
fermentation of the sugars in the juice during the three days
allowed for the fermentation process and the distillation efficiency.
A small part of the sugars is used during fermentation
by the yeast to produce new cells and grow and not all Ethanol
can be separated from water by the distillation process.
The starch extraction and saccharification efficiency
measured was 96 percent that is a very satisfactory value. The
fermentation efficiency measured based on the sugar content
of the slurry before and after fermentation was in the range of
84 percent. Therefore the total process efficiency of the used
method was about 81 percent.
It is evident that the process could be further optimized by
monitoring the cooking and saccharification times, the
amount and fabricate of enzymes and yeast used, the duration
of the fermentation, the temperature level at which fermentation
is taking place, etc. The efficiency of the process could be
also improved by applying additional yeast on the second or
third day of the fermentation and extending the time allowed
for the fermentation process. The optimization of the process
was nevertheless out of scope of the present work.
4.2. The prospects of using Ferula communis as an
energy plant
This work has shown that the flower stalks of the plant
F. communis could be used for ethanol production, although
the yield of 55.8 cm3 kg1 dry flower stalks is low, compared
to other materials like that of A. aestivus, 83.72 cm3 kg1
tubers, [8] or the theoretical yield of potatoes that ranges
100e120 cm3 kg1 tubers according to the starch content of the
variety [5]. For commercial applications, a method should be
found to increase the efficiency of juice extraction from the
stalks as happens by sugar canes. The case of F. communis is
more difficult due to the fibrous and solid construction of the
stalks. F. communis should be further studied so as to determine
its agronomic characteristics, like water requirements,
yield, cultivation and harvesting techniques, etc under Mediterranean
conditions [2]. The content of starch and fermentable
sugars in the flower stalks, as mentioned above, varies
considerably during the year depending on the life phase of
the plant. The optimum harvesting time should therefore be
estimated so as to maximize the ethanol yield. F. communis
could grow in degraded lands as a rain fed crop. A rough
estimation of the production would be 300e400 L of Ethanol
per hectare of land, based on a density of 2.8 plants per square
meter and 2 kg of stalks per plant. The study of the agronomic
performance of the plant was not within the scope of this
study. F. communis could be processed together with other
plants, like A. aestivus and Chrysanthemum coronarium, so as to
increase the efficiency of land use. The distillate wastes from
the process could be used, together with other biomass
material, as feedstock to a biogas reactor for the production of
biogas for electricity and heat generation. In addition, it has to
be examined to what extend the end byproduct could be used
in combination to other materials, for the production of
compost that would be a good source of organic matter to
degraded soils.
Acknowledgments
A lot of experience and related information was gained during
the execution of the “ENERGAL” project, TEXNO/0104/11 cofinanced
by the Cyprus Research Promotion Foundation
(CRPF), the ARI and the Institute of Energy of Cyprus. The
author would like to thank CRPF and the Institute of Energy of
Cyprus for co-financing the acquisition of the experimental
ethanol production unit CE640. The author would moreover
like to thank Mr. Michalis Elia, Mr. Moses Charalambous, Mr.
Louka Thrassos, Mr. Sozos Telemachou and Mr. Vaidis Ioannis
for their technical assistance.